SONIMUD

Acoustic (sonic) measurements are routinely used to evaluate the safe depth of navigation, Nautical depth, at the waterways and ports using dual beam echo sounder. The dual beam echo sounder measurements are usually carried using two frequency ranges 200-215 kHz and 15-40 kHz. The high frequency ranges 200-215 kHz are used to detect the top of the fluid mud layer. On the other hand, the low frequency ranges 15-40 kHz are used to locate the seafloor. However, one of the fundamental challenges facing the acoustic (sonic) measurements, in this environment, is the fundamental understanding of the dissipation of the acoustic signal in the Non-Newtonian fluid mud. This phenomenon makes existing acoustic methods not informative about the physical properties of the fluid mud.

Other non-acoustic measuring methods that can provide information about the strength of the fluid mud have several disadvantages. One distinct disadvantage is the relation between predicted strength properties and the tool’s measuring output, which is based on empirical relations. As a result, the tools must be calibrated for the specific location and conditions of the survey. Another drawback is that the available measuring techniques provide only point measurements; hence, the penetrometer measurements have low repeatability. This makes it impossible to monitor for temporal changes of the mud properties in the mud layer caused by a storm or dredging activities, for instance. Last, but not least, common measuring devices penetrate the mud, and, thus, alter the mechanical and rheological properties of the mud during the survey. This means that resulting strengths obtained from these devices will be different before, during, and after the survey even when measuring at the same location. All these arguments suggest that new reliable and more practical measuring techniques need to be developed within the SONIMUD project, which would allow conducting continuous non-invasive surveys. Currently, innovative geophysical methods are tested on the lab and 1:1 scale.

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